Wheat Development, Productivity, and Nitrogen Use Are Unaffected by Stable Isotope Form of the Nitrogen Source

Abstract

Under conditions where an adequate amount of isotopic 15N is supplied, it is not known whether wheat (Triticum aestivum) plants have a preference for 14N against the heavy isotope. A pot experiment was conducted for 2 yr with manually controlled nitrogen (N) supply to assess crop development, dry matter production, and N acquisition and partitioning in spring wheat plants grown in plastic pots filled with Ottawa sand. A set of plants were supplied with N from an 14N source (0.37 atom % 15N) throughout the growing period, while another set of plants received the same amounts of N from an 15N-enriched fertilizer source (91.2 atom % 15N). At crop maturity, about 60% of the applied 15N was recovered in different plant parts, and 65% of the total N content in the plant was enriched with 15N compared with <0.5% in the control treatment. There were not any visual differences between the two sets of plants; neither was there a difference in quantitative traits such as plant height, leaf greenness, dry matter production, N acquisition and partitioning. This study demonstrated that given similar concentrations of the two N treatments that differed markedly in their 15N enrichment, there was no differentiation in N uptake and partitioning resulting from isotopic enrichment of the two N sources. This indicated that there is no preference against 15N by the wheat plants, and the greater natural abundance of the 14N is the main reason why plant tissues are dominated with 14N isotope.

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